The Dark Side of Fiber (Part II of III)

The Dark Side of Fiber (Part II of III)

This is the second article of a third part series on fiber. This article examines if fiber is good for heart health and protecting against colon cancer. The first articleexamines if fiber is good for constipation and lowering cholesterol. The third article examines if fiber is good for Irritable Bowel Syndrome (IBS) and heartburn.

Can Fiber Improve My Heart Health?

Two studies, one based in Finland and one in Japan suggest that people who eat lots of fiber (30-35 grams per day) may reduce their risk of coronary heart disease[i]. I asked Gary Taubes, the author of Good Calories Bad Calories, about these studies. Gary cautioned me about reading too much into them. Observational studies follow large groups of people (22,000 subjects in the Finnish case, and 58,000 in the Japanese study) over time to see how their health develops. Then they compare, for example, the subgroup that ate the most fiber with the subgroup that ate the least, measure the occurrence of disease in each, and then draw conclusions about cause and effect connections.

He pointed out that the problem with this kind of study is that fiber consumption may not be the only factor shared by members of the subgroups. For example, the subgroup that ate more fiber may also be more health-conscious in general, and a more careful look at them might reveal that they also drink less, smoke less and / or exercise more. If true, this means that you cannot make a cause-and-effect connection between fiber consumption and heart health based on these studies (At least not without a lot more information about the individuals).

Gary’s point is that many hypotheses generated by observational studies later turn out not to be true, and setting broad dietary guidelines without randomized, placebo-controlled clinical studies can lead to unintended and sometimes unhealthy consequences.

Can Fiber Protect Me Against Colon Cancer?

The idea that high dietary fiber may lower the risk of colon cancer came from studies in the 1970s that made a connection between low colon cancer rates in developing countries and diets higher in fiber[ii]. A more recent study of 88,757 women found no association between dietary fiber consumption and the risk for colon cancer[iii]. Similar results were obtained from the Fukuoka Colorectal Cancer Study [iv] and another large study of men[v].

Can Too Much Fiber Promote Colon Cancer?

Alberto Martin’s recent study in Cell provides evidence that at least in mice susceptible to colon tumors, too much butyrate (gut bacteria ferment fiber to produce butyrate) promotes colon cancer and a low carbohydrate diet or inhibiting the growth of gut bacteria is protective. About 1/5 of human colon cancers have the same type of mutation as the mouse model they studied. [vi]

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Norm Robillard received his Ph.D. in microbiology from the University of Massachusetts, Amherst studying Bacillus anthracis and other Bacillus species. His post-doctoral training at Tufts University focused on antibiotic resistance and gene transfer between the gut microbes Bacteroides fragilis and E. coli.
During his career in pharma / biotech, Dr. Robillard studied the genetics of antibiotic resistance, septic shock, viral illnesses and antimicrobial and antibody-based therapies prior to founding the Digestive Health Institute. Dr. Robillard is the creator of the Fast Tract Diet, author of the Fast Tract Digestion book series and publisher of the Fast Tract Diet mobile app. He was the first to propose excess intestinal fermentation as the underlying cause of acid reflux and explained the connection between intragastric pressure from gas-producing bacteria in our intestines, nutritional malabsorption and the symptoms of acid reflux. His latest book series, Fast Tract Digestion provides a safe and effective dietary tool and behavioral strategy as an alternative to proton pump inhibitors (PPIs), H2 blockers, IBS drugs or antibiotics for heartburn, acid reflux, GERD, laryngopharyngeal reflux disease (LPR), IBS and other SIBO related conditions.

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